1. Health
Rachel Gurevich

Rate of Twins Greatly Increased Since 1980s, Older Moms and Fertility Treatment the Cause

By January 5, 2012

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Fertility drugs increase your risk of having twins, triplets, or more.

A new study from the CDC has found that the rate of twins has dramatically increased over the past three decades. Compared to 1980, the twin rate increased by 76% by 2009. While in 1980, 1 in 53 babies born were a twin, in 2009, 1 in every 30 babies born is a twin.

The reason seems to be caused by the use of fertility drugs, which boost your chances for multiples, and more women having children after age 35. Having a baby later in life increases your odds for twins. The CDC study found that the twin rate grew nearly 100% for women ages 35 and 39, and more than 200% for women age 40 and over.

An MSNBC.com article spoke about the increased rates of twinning, and their expert commented that the reason for more twinning after 35 may be due to older eggs, saying that older eggs may divide in abnormal ways.

This implied that the increase in twins for women over 35 is for monozygotic twins, or identical twins. In fact, that's inaccurate. The increased risk for twins over 35 is for dizygotic twins - non-identical twins. With monozygotic twins, one eggs splits, but with dizygotic twins, two different eggs are released and fertilized. (Learn more about the differences between monozygotic and dizygotic twins.)

Unless there's a study I'm not aware of, age is not connected to identical twin rates.

I wondered why the expert didn't explain that FSH, a hormone that plays an essential role in the ovulation, increases as a woman ages. FSH is the hormone that you inject with gonadotropin fertility treatments. While FSH increases because the eggs become less responsive as a woman ages, it does make some sense that there will be months when the eggs in the queue are eager to ovulate and more than one egg may get released.

It also just makes sense from a biological stand point. Fertility is going down, and the chances for any baby are decreasing. So the body makes a last ditch effort and starts releasing extras.

Did you conceive twins while taking fertility drugs? (I did! They're playing downstairs as I type, in fact!) Are you hopeful or worried about conceiving twins during treatment? Do you think the increased rate of twinning is a good, bad thing, or neither? Please feel free to share in the comments below.

Learn more about twins:

Photo (c) Craig Smallish / Getty Images

January 12, 2012 at 10:47 am
(1) Lorie says:

I had heard that twins are more common now due to fertility treatments. I’m on clomid for the first time this month, and truly hoping that we can have twins as an added bonus, but we’d be overjoyed with just one. I am in my 40′s, and DH is as well. Second marriages offer new beginnings, and perhaps women are also making the choice to start a second family.

January 18, 2012 at 3:52 am
(2) Raya says:

Such a nice article! Esp. the playing-downstairs-twins part. Thanks. :)

January 23, 2012 at 12:13 am
(3) Vuvu582 says:

I don’t see any thing wrong in increasing rate of twinning,and it’s a blessing from God 2 have a baby!

January 25, 2012 at 8:32 pm
(4) Kylenn says:

It’s great to have kids, but 7 billion people and growing exponentially is only gonna add to the problems. I hope people will find happiness in the deepening struggles we’ll be facing…

January 30, 2012 at 11:41 am
(5) Milind Shah says:

Having twins may play well with our society’s modern needs. So many couples are having kids at a later age but still want full families. It’s oddly efficient, isn’t it?

I watch my twins girls be the best friends possible to each other. I can’t imagine life could be better and would love for every family to experience that.

Meanwhile, we get to sleep later because the girls entertain themselves. This might be reason enough to wish for twins. ;)

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